The following paragraphs are provided by way of background to the present disclosure. They are not however an admission that anything discussed therein is prior art or part of the knowledge of persons skilled in the art.
Plants are capable of producing alkaloid compounds in small amounts. In general, these alkaloid compounds are relatively complex organic molecules, containing mostly basic nitrogen atoms. The in planta biosynthesis of an alkaloid compound involves the occurrence of a series of contiguous chemical reactions together constituting a so-called biosynthetic pathway. Each chemical reaction within a biosynthetic pathway is catalyzed by a different plant enzyme, and therefore alkaloid biosynthesis requires that plant enzymes and genes encoding these enzymes, act in concert within the plant cells. Well known examples of plants producing alkaloid compounds, are plants belonging to the Papaveraceae, a plant family constituting approximately 250 species and found mainly in mild and temperate regions of the world. Many alkaloid compounds have been found to have pharmacological effects and have been found useful, as medicinal compounds, as well as recreational drugs or stimulants. Examples of plant alkaloid compounds include the stimulants caffeine and nicotine, the stimulant and local anesthetic cocaine, the anti-malarial drug quinine, the analgesic morphine, the antimicrobials sanguinerine and berberine, the muscle relaxant papaverine and the cough suppressant noscapine.
Currently alkaloid compounds may be harvested from natural sources, such as opium poppy. Alternatively these compounds may be prepared synthetically. The existing manufacturing methods for alkaloid compounds however suffer from low yields and/or are expensive. For example, less than 2% of exogenous (R,S)-norlaudanosoline was converted to sanguinarine via a pathway of 10 genes from opium poppy (Papaver somniferum) re-assembled in yeast (Saccharomyces cerevisiae) (Fossati et al., 2014). An alternative approach to manufacturing plant alkaloid compounds would comprise marshaling a genetically modified host, e.g. a bacterial or yeast fermentation system, to produce alkaloid compounds. Such a biosynthetic system would permit inexpensive production of plant alkaloids in a tightly controlled environment. However due to the unusual complexity of the synthesis of the vast majority of desirable alkaloid compounds, methods for biosynthesis of alkaloid compounds using inexpensive nutrients and a genetically engineered host system to synthesize alkaloids from such nutrients, are not available. These complexities arise in part from the total number of separate chemical reactions included in a biosynthetic alkaloid production system. Inefficiencies in the performance of each reaction, starting from an economically available substrate, effectively are amplified along the chain of contiguous enzymes, thereby substantially compromising the yield of a final desired alkaloid product.
Thus is unclear whether and how existing methodologies may be used to achieve commercial biosynthesis of plant alkaloid compounds and their derivatives. There exists therefore in the art a need for improved methods for the biosynthesis of alkaloid compounds.